Another mild and sunny day

November 2010 was a fairly dry month, but that is the only weather feature it shared with this November. So far this month there have been no air frosts, although tonight could change that statistic. There have been several mild and sunny days, a continuing characteristic of this autumn, and although the leaves have fallen off most of the trees, the run up to winter is very different from last year. On this day in 2010, it was cloudy, not unusual of course, but the maximum temperature was only 1.4 Celsius. That is 12.7 Celsius lower than the highest temperature recorded today. Although a frost is a possibility for tonight, the minimum will undoubtedly be several degrees higher than on the corresponding night last year. On that night the temperature fell to minus 5.9 Celsius, the lowest November reading for 21 years. On the last day of the month there was heavy snow, and the good folk of this area awoke on the 1st of December to an 8 centimetre covering of snow! Not so this year, presumably.

The splendid weather has to end

Although no records have been broken, this month will be remembered for many dry, sunny and pleasantly warm days, and of course the exceptional heat at the beginning of October. At the moment it is the driest October since 1978, although rain tonight looks like changing that. October 1978, despite being a dry month, was not particularly sunny, and although days were often warm, nights were sometimes quite chilly. The cool nights have been a feature of recent temperature statistics this October, and that has dragged down the temperature averages. Therefore, it seems unlikely that this month will hold on to it's 5th warmest ranking (since 1900) . However, the 4 mildest Octobers have all occurred during the last 16 years and Edwardian or Georgian London would have been very pleased with this mild, bright and smog-free month!

1976 and all that

The grass is beginning to turn brown quite widely, just as it did during the summer of 1976. If the media were to believed in those hot and dusty days England would never again be a green and pleasant land. Of course, the rain arrived in spades late in August and through September. By the end of autumn, there was little to show for the prolonged dry spell. Aside, that is, for a few dead trees, most of which weren't native to southern England. So, where does it leave 2011? Although, it was the driest Spring this year in living memory and beyond in this area, the winter was fairly wet. Already this year we've had over 50mm more rain than we had in the first 6 months of 1976. Also, the weather patterns showed marked differences between the Springs of 1976 and 2011. As a result temperatures are very different. March 1976 was cooler than March this year with no days exceeding 16 Celsius (5 this year). April 1976 had near normal temperatures compared to the record-breaking warmth this year. By way of contrast, May was fairly warm in 1976 with the temperature exceeding 29 Celsius as early as the 7th. Although this May was reasonably warm there were no hot days. June 1976 was outstandingly warm, and although the maximum temperature today is around 27, a decline into maxima mediocrity seems imminent.

Now it's seriously dry.

A few spots of rain fell this morning but now it's beginning to look very dry. The trees are losing their Spring lustre and the grass is turning increasingly brown. It's not surprising really. The total rainfall for this area since 1st March (66 days) is only 21.6 mm. To put that figure into context, the 20-year average fall for those 66 days in this area is 105mm, so the total this year is only just over 20% of the average. What of the rest of Spring? Will it beat the record? Interestingly, the average rainfall for the first 15 days of May is 15mm, but for the last 16 days of May the average is 29mm. Therefore, if 'average' rainfall occurs for the last 16 days of the month the record will not be broken! The total for the Spring would then be around 51mm which would rank this Spring as the 6th driest since 1900. However, if only 18mm of rain falls the record will be broken. In 4 of the last 20 years, and 21 of the last 110 years, there have been daily falls of over 20mm in this area during May. So, it only takes one big thunderstorm and that 'Dry Spring' record set in 1976 remains intact.....and by the way, the grass really did turn brown by the end of that Summer, all of it!

April 2011....a remarkable month

April 2011 was a sunny month, about the 15th sunniest since 1900. It was also a dry month, the 2nd driest since 1900 behind the April of 1938. It was also the driest early Spring (March/April combined) since 1938. However, the most remarkable feature about April 2011 was the temperature. It was the warmest April since reliable instrument records began in the 19th century, and in doing so beat the outstandingly warm April of 2007. To put the event into perspective statistically; the mean temperature for April 2007 was 13.0, which was a massive 1.4 Celsius higher than the previous record set in 1943. The mean temperature for April 2011 was 13.6! If the month was May instead of April it would have been ranked the 21st warmest May since 1900. The very dry ground aided overnight cooling, and although no air frosts occurred, the mean minimum temperature was only 2.5 Celsius above normal. The mean maximum temperature (19.3) was 4.9 Celsius above normal. This figure was truly incredible. Since 1900, there have only been 8 Mays with higher average maxima. None of these warmer Mays occurred between 1923 and 1988 inclusive. Not only were April 2011 days warmer than most May days, there were several summer months in recent years that have been cooler by day: namely the Junes of 1953,1954,1955,1956,1971,1972,1977,1978,1979,1980,1981,1985,1987,1988 and 1991: the Julys of 1954 and 1980; and the Augusts of 1956 and 1963. What next?

The end of the dry spell

After 17 days without measurable rain, the 0.2 millimetres that fell yesterday evening was enough to break the dry spell. Most years have a prolonged dry spell (15 days or longer) with Spring and Autumn months most likely to see one. September and the beginning of October have had 3 dry spells in recent years. 1997, 2002 and 2007 each had between 15 and 17 consecutive dry days, and back in 1969 only 3 millimetres of rain fell throughout September. The most prolonged autumn dry spell in the London area occurred from the 14th September to 9th October 1921 (26 days). However, there were several lengthy dry periods that began in August, notably 23rd August to 28th September 1929, and 15th August to 20th September 1959, both 37 days. In the extended good summer of 1959 there was a further 17 days of dry weather from the 23rd September until 9th October.